Connector assemblies which include means for receiving a miniature quartz halogen or similar light bulb in order to provide a light source for a fiber optic equipped dental handpiece are well known from the prior art. It is also a well recognized that in order to achieve the necessary brightness for the job at hand, the quartz halogen bulbs must operate at a high burning temperature, preferably in the range of 2500.degree.-2900.degree. F. However, such high operating temperatures generate an excessive amount of radiant heat which result in the dental handpiece and connector becoming uncomfortable to handle for prolonged periods of use.
U.S. Pat. No. 4,334,863 issued to Kenneth S. Magid et al. discloses a three element dental handpiece illuminator system which attempts to balance the above described brightness and overheating problem associated with use of a quartz halogen bulb. The illuminator system includes: (1) a replaceable plug-in cartridge having a small quartz halogen lamp enclosed therein; (2) an adaptor unit disposed permanently connected to the air/water/power supply hose; and (3) a cylindrical outer shield member which encloses both the adaptor and plug-in cartridge and couples the entire three element illuminator system to the threaded end of the dental handpiece connector. Both the adaptor and plug-in cartridge have a plurality of longitudinally oriented fluid transmitting channels or conduits which correspond in configuration to the fluid conduits of the dental handpiece. The quartz halogen bulb of Magid is permanently mounted within an internal axially aligned socket of the plug-in cartridge.
Magid teaches to prevent excess temperature rise of the illuminator in two ways. First, there is provided an air space between the bulb and its surrounding socket wall and second, there is an air space provided between the outer peripheral surface of the plug-in cartridge and the surrounding cylindrical housing. The two air spaces absorb the radiant heat transfer from the bulb to the plug-in cartridge and from the plug-in cartridge to the outer cylindrical housing, respectively. Magid also teaches that this radiant heat absorbed by the air space is cooled or carried away by the continuous flow of air and water through the fluid conduits of the plug-in cartridge. In other words, Magid suggests to maintain the temperature of the illuminator at a tolerable level by convection heat transfer wherein the air heated by the halogen bulb is carried off by the drive air, exhaust air, and/or water coolant which are continuously transmitted through the illuminator during use of the dental handpiece.
In a commercial embodiment of the illuminator constructed in accordance with the Magid patent, the socket for the bulb is in direct air communication with the drive air and exhaust air conduits of the plug-in unit. This is done presumably to set up the desired connection heat transfer to maintain the outside surface temperature of the connector at or below a predetermined a tolerable level. In order to replace the halogen bulb, the entire plug-in cartridge is removed and discarded in favor of a new plug-in cartridge with enclosed bulb. This requires the user to repeatedly break the air/water and electrical connections between the plug-in cartridge and the adapter interface. Over time, the repeated disconnections tend to cause leaks in the adjacent gasket seal, land as a result, corrosion of the electrical connections in this region is likely to occur. This arrangement also adversely affects the operating life of the bulb, since the lubricants present in the turbine head of the dental handpiece eventually find their way into the exhaust air stream, and this results in the formation of a lubricant mist which eventually contacts and coats the bulb. This, in turn, leads to premature dimness and eventual failure of the bulb.
U.S. Pat. No. 4,330,274 issued to Friedman et al. discloses a dental handpiece illuminator system which is similar in design in the Magid system in that it also includes a generally cylindrical connector unit having a socket for containing a halogen bulb and an outer cylindrical shield member for enclosing the connector unit. Also, like the Magid design, the shield member of Friedman includes threads disposed along an inner surface at one end for threaded engagement with the external threads of the dental handpiece. The connector unit includes a spring-loaded bulb socket for convenient bulb replacement. Friedman teaches to permanently secure one end of the connector unit to the air/water and electric power supply tubing in order to overcome the problems of leaky seals and corrosion of adjacent electrical contacts caused by the required repeated disconnection of a plug-in type cartridge unit from the air/water and electrical supply tubing of other prior art designs.
In both the dental handpiece illuminator system of Magid and Friedman, the user must unscrew the outer shield member from the handpiece to get at the connector unit or plug-in cartridge to replace a burned out light bulb. The time required to replace a bulb in these systems may be unacceptably long and therefore may discourage some dentists from continuing to use such an illumination system. While quick disconnect assemblies for dental handpiece connectors are generally known in the art, these prior art quick disconnect assemblies use a centered axial plug-type connection, similar in design to a common high pressure air hose. However, in view of the many design difficulties associated with the proper alignment and isolation of the optical pathway and light bulb socket with respect to the fluid transmitting channels of the connector unit, such central, axial plug-type quick disconnect coupling assemblies have not yet been successfully implemented in a conventional illuminated connector assembly for fluid driven, fiber optic dental handpieces.